Nomad, I'm thinking it's time to bring out the big guns.
Dirt bags have nothing to lose, but us responsible people don't get that because we can't relate so we jump through hoops trying to do the right thing, try to mitigate the damage, with people who just don't have one moral bone in their bodies, happens so often in the legal system.
First I would call the chief of police to request an official discussion as to why that man was able to pull a knife on a disabled person and not be removed from her home and charged criminally, as he should have, period. They need to answer for this, not with some bs about it being a civil matter but why a threat like that was disregarded, the chief should be put on notice for this. And I would let the police chief know how the HOA and neighbors are very concerned about this situation and how "they, the police department" let it continue. Let them start to squirm a bit, while they wait for the next call they are going to know is coming after you alerted them of the concern now from the neighbors. Law enforcement should not push criminal behavior onto a civil matter, and that's what they did here, so put their butts on notice. I know what I am talking about here.
And then I would turn off the electricity and the water, internet anything else in that apartment, now. Legally, who the hell cares, you go in front of a judge with a blank look on your face and say "oh judge, but my daughter doesn't live there because squatters pushed her out." and if he says turn it all back on say "okay as soon as I can" and then do nothing. Nothing legally will happen to you, period. You can go back in the next time and say "oh, you want me to turn on what? Oh, okay." and do nothing again. But it won't get that far, because dirt bags don't take you to court, you take them to court.
That dirt bag is going to steal and trash anything he can on the way out, no matter what you do or don't do in his favor, he knows what he's doing, you can't "nice" him into not tearing out the plumbing or whatever, when he goes. Just get it over with as soon as you can. Make it as uncomfortable for him as you can with the living situation, with the HOA and the neighbors and the police.
And then after this storm deal with not allowing this to happen again from your daughters side.
And please don't let all of the work you have done to make a nice place for your daughter take you under, it's just things. You worked hard, very hard, to create a beautiful place for your daughter. Your health is so much more important than that. And maybe right now it's not what she needs, to feel as if she owns it herself. I go into my son's apartment and want to start cleaning and picking up, straightening up, bring over the carpet cleaner and organize, create a space as he grew up in, so I get it. But he's proud of it because of the lights he's strung and the wall hangings he's put up. A place that's basically livable is really all your daughter needs, not your dream for her but maybe her space as it is that she can handle for herself.